Who was the closest person to the Prophet of Islam (PBUH)?

SHAFAQNA -Imam Ali said: I was with the Prophet (PBUH) in Hira Cave; I could see the light of the prophethood and smell it. I heard that painful groan of the Satan when revelation was sent down to the Prophet (PBUH). I asked the Prophet (PBUH) what is this groan? The Prophet (PBUH) replied: “This groan is the groan of the Satan who has lost all hopes of being worshipped.” Then the Prophet (PBUH) told me: “O’ Ali (AS), you hear whatever I hear; and you see whatever I see, except that you are not a prophet” [1].